GAK_Q56.TIF - Gulf of Alaska U.S. EEZ GLORIA sidescan-sonar data mosaic (26 of 30) (LCC, 50 m, WGS84)

Metadata also available as - [Outline] - [Parseable text]

Frequently-anticipated questions:

What does this data set describe?

Title:
GAK_Q56.TIF - Gulf of Alaska U.S. EEZ GLORIA sidescan-sonar data mosaic (26 of 30) (LCC, 50 m, WGS84)
Abstract:
GLORIA data for the Gulf of Alaska Exclusive Economic Zone (EEZ) were acquired during five cruises over a four year period. The first cruise conducted in 1986 (F-1-86-GA) surveyed an area of the north-central mosaic area and covered an area of approximately 40,000 square kilometers (sq km). The second two cruises (F-8-88-AA, F-9-88-WG) were conducted in 1988. One of the 1988 cruises (F-8-88-AA) focused on a survey of the Aleutian Arc. The eastern most portion of that survey extended outside of the Aleutian Arc survey area and covered an area of approximately 52,000 square kilometers (sq km) of seafloor on the western edge of the Gulf of Alaska. The final two cruises (F-6-89-GA, F-7-89-EG) were completed in 1989. As in earlier EEZ reconnaissance surveys, the USGS utilized the GLORIA (Geological LOng-Range Inclined Asdic) sidescan-sonar system to complete the geologic mapping. The collected GLORIA data were processed and digitally mosaicked to produce continuous imagery of the seafloor. Thirty digital mosaics with a 50-meter pixel resolution were completed for the region.
  1. How should this data set be cited?

    U.S. Geological Survey, 2011, GAK_Q56.TIF - Gulf of Alaska U.S. EEZ GLORIA sidescan-sonar data mosaic (26 of 30) (LCC, 50 m, WGS84): Open-File Report 2010-1332, U.S. Geological Survey, Coastal and Marine Geology Program, Pacific Coastal and Marine Science Center, Menlo Park, CA.

    Online Links:

    This is part of the following larger work.

    Paskevich, Valerie F. , Wong, Florence L. , O'Malley, John J. , Stevenson, Andrew J. , and Gutmacher, Christina E. , 2011, GLORIA Sidescan-Sonar Imagery for Parts of the U.S. Exclusive Economic Zone and Adjacent Areas.: Open-File Report 2010-1332, U.S. Geological Survey, Coastal and Marine Geology Program, Pacific Coastal and Marine Science Center, Menlo Park, CA.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -138.295750
    East_Bounding_Coordinate: -134.537069
    North_Bounding_Coordinate: 57.173657
    South_Bounding_Coordinate: 54.817805

  3. What does it look like?

    <https://pubs.usgs.gov/of/2010/1332/gloria_data/gulf_of_alaska/browse/gak_q56-thumb.gif> (GIF)
    Thumbnail image showing an overview of the Gulf of Alaska U.S. EEZ GLORIA mosaic 56.
    <https://pubs.usgs.gov/of/2010/1332/gloria_data/gulf_of_alaska/browse/gak_q56.gif> (GIF)
    Browse image showing an overview of the Gulf of Alaska U.S. EEZ GLORIA mosaic 56.

  4. Does the data set describe conditions during a particular time period?

    Beginning_Date: 24-Jun-1986, 19880706, 19880805, 19890516, 19890614
    Ending_Date: 03-Jul-1986, 19880802, 19880831, 19890612, 19890710
    Currentness_Reference: ground condition

  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form: remote-sensing image

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

      This is a Raster data set. It contains the following raster data types:

      • Dimensions 4813 x 4184 x 1, type Pixel

    2. What coordinate system is used to represent geographic features?

      The map projection used is Lambert Conformal Conic.

      Projection parameters:
      Standard_Parallel: 50.000000
      Standard_Parallel: 59.000000
      Longitude_of_Central_Meridian: -144.000000
      Latitude_of_Projection_Origin: 0.000000
      False_Easting: 0.000000
      False_Northing: 0.000000

      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 50.000000
      Ordinates (y-coordinates) are specified to the nearest 50.000000
      Planar coordinates are specified in meters

      The horizontal datum used is D_WGS_1984.
      The ellipsoid used is WGS_1984.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257224.

  7. How does the data set describe geographic features?

    Entity_and_Attribute_Overview:
    There are no attributes associated with a GeoTIFF image. Image pixel values contain acoustic reflectivity values normalized to an 8-bit data range (0-255). Low-backscatter is represented by dark tones (low values), and high-backscatter is represented by bright tones (high values).

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)

  2. Who also contributed to the data set?

    The U.S. Geological Survey (USGS) must be referenced as the originator of the dataset in any future products or research derived from these data.

  3. To whom should users address questions about the data?

    U.S. Geological Survey
    c/o Florence Wong
    Geologist
    345 Middlefield Road MS 999
    Menlo Park, CA 94025
    USA

    (650) 329-5327 (voice)
    (650) 329-5198 (FAX)
    fwong@usgs.gov

Why was the data set created?

This remote sensing image of the seafloor is 26 of 30 mosaics created from GLORIA sidescan-sonar data covering the Gulf of Alaska.

How was the data set created?

  1. From what previous works were the data drawn?

    GLORIA pass data (source 1 of 1)
    Type_of_Source_Media: digital tape media
    Source_Contribution:
    GLORIA data were logged to magnetic tape in 6-hour portions referred to as "passes". Each completed pass contained a maximum 720 "lines" of data at the usual 30-second pulse repetition rate. Each line consisted of a 1024 byte record that contained the port and starboard returns from a single ping as well as header information. These "passes" contained geometric and radiometric distortions which had to be corrected before they could be digitally mosaicked.

  2. How were the data generated, processed, and modified?

    Date: Unknown (process 1 of 13)
    The GLORIA "passes" necessary to complete the mosaic were retrieved from magnetic tape. Navigation data were merged into the individual "passes" to update the header information with depth and location coordinates.

    Person who carried out this activity:

    U.S. Geological Survey
    345 Middlefield Road MS 999
    Menlo Park, CA 94025
    USA

    (650) 329-5078 (voice)
    (650) 329-5190 (FAX)

    Data sources used in this process:
    • GLORIA pass data

    Data sources produced in this process:

    • "pass".mrg

    Date: Unknown (process 2 of 13)
    Slant-Range correction, the first of two geometric corrections, were applied to the "passes". Slant-range error is mislocation of pixels in the cross-track direction compared to their proper location on a map. This error occurs due to the way that the sidescan-sonar senses distance to a target. After the slant-range correction has been made, the across-track location of targets is accurate.

    Person who carried out this activity:

    U.S. Geological Survey
    345 Middlefield Road MS 999
    Menlo Park, CA 94025
    USA

    (650) 329-5078 (voice)
    (650) 329-5190 (FAX)

    Data sources used in this process:
    • "pass".mrg

    Data sources produced in this process:

    • "pass".slr

    Date: Unknown (process 3 of 13)
    A series of radiometric corrections were then applied to the "passes". The first enhancement was used to correct for shading problems that occur in the across-track direction and are a function of attenuation in range distance and transmitter power build-up.

    Person who carried out this activity:

    U.S. Geological Survey
    345 Middlefield Road MS 999
    Menlo Park, CA 94025
    USA

    (650) 329-5078 (voice)
    (650) 329-5190 (FAX)

    Data sources used in this process:
    • "pass".slr

    Data sources produced in this process:

    • "pass".shd

    Date: Unknown (process 4 of 13)
    The next radiometric enhancement was applied in a two-part filtering process to remove the striped noise that can be found in side-scan sonar image in the across-track direction. The noise was removed by applying two separate boxcar filters: (1) a high-pass filter that will contain the high-frequency component of the image without the noise; and (2) a low-pass filter that will include the low-frequency component of the image without the noise.

    Person who carried out this activity:

    U.S. Geological Survey
    345 Middlefield Road MS 999
    Menlo Park, CA 94025
    USA

    (650) 329-5078 (voice)
    (650) 329-5190 (FAX)

    Data sources used in this process:
    • "pass".shd

    Data sources produced in this process:

    • "pass".hpf
    • "pass".lpf

    Date: Unknown (process 5 of 13)
    The two filtered images were combined to recreate an image similar to the original but without the noise.

    Person who carried out this activity:

    U.S. Geological Survey
    345 Middlefield Road MS 999
    Menlo Park, CA 94025
    USA

    (650) 329-5078 (voice)
    (650) 329-5190 (FAX)

    Data sources used in this process:
    • "pass".lpf
    • "pass".hpf

    Data sources produced in this process:

    • "pass".wco

    Date: Unknown (process 6 of 13)
    The second geometric correction, aspect-ratio distortion, was applied to the "passes". The aspect-ratio distortion was removed by using the navigation data to compute the distance traveled by the ship. Given the distance traveled, the number of pixels (each representing 50 m) required along the particular segment was calculated. The original pixels were then duplicated the appropriate number of times to fill the space with 50-meter pixels and thus achieve a 1:1 ratio between along-track and across-track distances. The practice of duplication to create a square 50-meter pixel size was followed so that information in the across-track direction would not have to be omitted.

    Person who carried out this activity:

    U.S. Geological Survey
    345 Middlefield Road MS 999
    Menlo Park, CA 94025
    USA

    (650) 329-5078 (voice)
    (650) 329-5190 (FAX)

    Data sources used in this process:
    • "pass".wco

    Data sources produced in this process:

    • "pass".vel

    Date: Unknown (process 7 of 13)
    A third radiometric enhancement, a 2 by 2 low-pass filter for smoothing the images, was applied to the "passes". Because the delta velocity correction typically stretches the imagery 1:2.5 times, a 2 by 2 low-pass filter is applied to the image to smooth and reduce the blockiness that results from the line duplication. The 2 by 2 low-pass filter smoothes out the blockiness introduced into the image without over smoothing and blurring the image.

    Person who carried out this activity:

    U.S. Geological Survey
    345 Middlefield Road MS 999
    Menlo Park, CA 94025
    USA

    (650) 329-5078 (voice)
    (650) 329-5190 (FAX)

    Data sources used in this process:
    • "pass".vel

    Data sources produced in this process:

    • "pass".2b2

    Date: Unknown (process 8 of 13)
    A final radiometric enhancement was applied to the image to reduce the halo effect that occurs in the along-track direction near the nadir. This enhancement involved creating two separate images from the input image. The images were produced as a result of 151-line by 31- sample high-pass filter plus a 151-line by 401-sample low-pass filter. The two resultant images were then digitally combined to produce an image similar to the original but without the halo effect.

    Person who carried out this activity:

    U.S. Geological Survey
    345 Middlefield Road MS 999
    Menlo Park, CA 94025
    USA

    (650) 329-5055 (voice)
    (650) 329-5190 (FAX)

    Data sources used in this process:
    • "pass".2b2

    Data sources produced in this process:

    • "pass".hal

    Date: Unknown (process 9 of 13)
    After the geometric and radiometric corrections were applied, the data were ready for the digital mosaicking. The necessary segments of processed data, each representing about 6-hours of data acquisition, were spliced end-to-end to make continuous swaths for portions of the tracklines where the ship's heading remained generally constant and passed through the mosaic area. The segments were tone-matched by adjusting the average brightness to minimize the tonal contrast at the seams where they were joined. Latitude, longitude, and heading were determined along the trackline of each continuous segment of data at the start, end, and two intermediate points. These four control points, with eight additional points that were computed for the edges of the image segment, were used to position the segment within the map grid.

    Person who carried out this activity:

    U.S. Geological Survey
    345 Middlefield Road MS 999
    Menlo Park, CA 94025
    USA

    (650) 329-5078 (voice)
    (650) 329-5190 (FAX)

    Data sources used in this process:
    • "pass".hal

    Data sources produced in this process:

    • gak_q56_line"n"

    Date: Unknown (process 10 of 13)
    When the individual trackline segments had been georeferenced, the next step was to digitally stencil the segments to remove unwanted data (i.e. noise). Interactively, a line was drawn on a video display outlining the portion of each image segment to be retained while comparing it to adjacent segments. Then all pixels outside the area enclosed by the line were converted to zero values, thereby retaining only that portion of the image desired. Finally, each stenciled segment was mosaicked to adjacent segments, sequentially building the composite map. In this way a digital file was created with the desired map projection for each imagery sheet (mosaic).

    Person who carried out this activity:

    U.S. Geological Survey
    345 Middlefield Road MS 999
    Menlo Park, CA 94025
    USA

    (650) 329-5078 (voice)
    (650) 329-5190 (FAX)

    Data sources used in this process:
    • gak_q56_line"n"

    Data sources produced in this process:

    • gak_q56

    Date: 22-Aug-2007 (process 11 of 13)
    The binary image files of the GLORIA mosaics were imported into a PCI database file allowing the images to be georeferenced. The image georeference report was saved for future reference.

    Person who carried out this activity:

    U.S. Geological Survey
    c/o Valerie Paskevich
    384 Woods Hole Road
    Woods Hole, MA 02543-1598
    USA

    (508) 548-8700 (voice)

    Data sources used in this process:
    • gak_q56.bin

    Data sources produced in this process:

    • gak_q56.pix; channel 1
    • gak_q56-georep.txt

    Date: 22-Aug-2007 (process 12 of 13)
    The GLORIA image was exported from the PCI database file to a GeoTIFF image with an accompanying world file.

    Person who carried out this activity:

    U.S. Geological Survey
    c/o Valerie Paskevich
    384 Woods Hole Road
    Woods Hole, MA 02543-1598
    USA

    (508) 548-8700 (voice)

    Data sources used in this process:
    • gak_q56.pix; channel 2

    Data sources produced in this process:

    • gak_q56.tif
    • gak_q56.tfw

    Date: 22-Aug-2007 (process 13 of 13)
    The image was modified to flood-fill the background 0 (black) data value to 255 (white). After modification, the header portion of the image was updated to restore the georeferencing information.

    Person who carried out this activity:

    U.S. Geological Survey
    c/o Valerie Paskevich
    384 Woods Hole Road
    Woods Hole, MA 02543-1598
    USA

    (508) 548-8700 (voice)

    Data sources used in this process:
    • gak_q56.tif
    • gak_q56.tfw

    Data sources produced in this process:

    • gak_q56.tif
    • gak_q56.tfw

  3. What similar or related data should the user be aware of?

    (editor), J.V. Gardner , (editor), M.E. Field , and (editor), D.C. Twichell , 1996, Geology of the United States Seafloor: The View from GLORIA: Cambridge University Press, Cambridge, U.K..

    Jr., P.S. Chavez , 1986, Processing Techniques for Digital Sonar Images from GLORIA: Photogrammetric Engineering and Remote Sensing Vol. 52, No. 8, August 1986, p. 1133-1145, American Society for Photogrammetry and Remote Sensing, Falls Church, VA 22046.

    Jr., P.S. Chavez , 1984, U.S. Geological Survey mini image processing system (MIPS): Open-File Report 88-880, U.S. Geological Survey, Reston, VA.

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?

    There are no attributes associated with a GeoTIFF image.

  2. How accurate are the geographic locations?

    Primary navigational control for this survey was by Loran-C supplemented by satellite navigation. Accuracy of location of the navigation fixes is estimated to be better than 100 meters.

  3. How accurate are the heights or depths?

  4. Where are the gaps in the data? What is missing?

    All available imagery were used to create this mosaic. Data were acquired during four cruises using the 6.5 kHz GLORIA sidescan-sonar system and a 45-km total swath width.

  5. How consistent are the relationships among the observations, including topology?

    not applicable

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints: None
Use_Constraints:
Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey as the originator of the dataset.

  1. Who distributes the data set? (Distributor 1 of 2)

    U.S. Geological Survey
    345 Middlefield Road MS 999
    Menlo Park, CA 94025
    USA

    (650) 329-5078 (voice)
    (650) 329-5190 (FAX)

  2. What's the catalog number I need to order this data set?

    Downloadable Data

  3. What legal disclaimers am I supposed to read?

    Neither the U.S. Government, the Department of the Interior, nor the USGS, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

  4. How can I download or order the data?

  5. What hardware or software do I need in order to use the data set?

    The sidescan-sonar mosaic is available as a GeoTIFF image with accompanying world file and georeference report. To utilize this data, the user must have an image viewer, image processing or GIS software package capable of importing a GeoTIFF image. If the georeferencing information cannot be imported, the user may wish to obtain the georeference information contained in a separate file included in the zip file.

  1. Who distributes the data set? (Distributor 2 of 2)

    U.S. Geological Survey
    384 Woods Hole Road
    Woods Hole, MA 02543-1598
    USA

    (650) 329-5078 (voice)
    (650) 329-5190 (FAX)

  2. What's the catalog number I need to order this data set?

    Downloadable Data

  3. What legal disclaimers am I supposed to read?

    Neither the U.S. Government, the Department of the Interior, nor the USGS, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

  4. How can I download or order the data?

  5. What hardware or software do I need in order to use the data set?

    The sidescan-sonar mosaic is available as a GeoTIFF image with accompanying world file and georeference report. To utilize this data, the user must have an image viewer, image processing or GIS software package capable of importing a GeoTIFF image. If the georeferencing information cannot be imported, the user may wish to obtain the georeference information contained in a separate file included in the zip file.

Who wrote the metadata?

Dates:
Last modified: 31-Mar-2011
Metadata author:
U.S. Geological Survey
c/o Valerie Paskevich
Information Specialist / GIS Coordinator, retired
384 Woods Hole Road
Woods Hole, MA 02543-1598
USA

(508) 548-8700 (voice)
(508) 457-2310 (FAX)

Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:

Generated by mp version 2.9.8 on Thu Mar 31 11:41:33 2011